Apparatus and method for filtering event signals

Abstract

A system for filtering multiple event signals from multiple event-generating sources. A selection circuit receives the multiple event signals and selects one of the event signals. A filter circuit is coupled to the selection circuit and receives the selected event signal from the selection circuit. The filter circuit produces a filtered event signal. A counter receives the filtered event signal from the filter circuit and is incremented in response to the filtered event signal. The filter circuit includes a comparison logic circuit and an edge detection logic circuit.

What is claimed is: 
     
       1. An apparatus for filtering event signals in a processing system comprising: a selection circuit coupled to receive a plurality of event signals and select one of said event signals;   a filter circuit coupled to said selection circuit and receiving said selected event signal, said filter circuit generating a filtered event signal; and   a counter coupled to said filter circuit, said counter incremented in response to said filtered event signal.   
     
     
       2. The apparatus of claim 1 further including a multiplexer coupled to said filter circuit and said selection circuit, wherein said multiplexer selects between signals from said selection circuit and said filter circuit. 
     
     
       3. The apparatus of claim 1 wherein said selection circuit includes a multiplexer coupled to receive said plurality of event signals. 
     
     
       4. The apparatus of claim 1 wherein said selection circuit includes a plurality of tri-state drivers coupled to receive said plurality of event signals. 
     
     
       5. The apparatus of claim 1 wherein said filter circuit includes a comparison circuit for comparing said selected event signal with a counter mask. 
     
     
       6. The apparatus of claim 5 wherein said comparison circuit includes an inversion circuit capable of inverting a comparison circuit output in response to an inversion signal. 
     
     
       7. The apparatus of claim 1 wherein said filter circuit includes an edge detection circuit. 
     
     
       8. The apparatus of claim 7 wherein said edge detection circuit includes a latch coupled to an input of an AND gate. 
     
     
       9. The apparatus of claim 1 wherein said filter circuit includes a comparison circuit coupled to an edge detection circuit. 
     
     
       10. The apparatus of claim 9 further including a multiplexer coupled to said comparison circuit, said edge detection circuit, and said selection circuit, wherein said multiplexer selects between signals from said selection circuit and said filter circuit. 
     
     
       11. An apparatus for filtering event signals comprising: a selection circuit having a plurality of inputs coupled to a plurality of event-generating sources;   a filter circuit coupled to an output of said selection circuit, said filter circuit adapted to generate a filtered event signal; and   a counter coupled to said filter circuit, said counter incremented in response to said filtered event signal.   
     
     
       12. The apparatus of claim 11 wherein said filter circuit includes a comparison circuit for comparing said selected event signal with a counter mask. 
     
     
       13. The apparatus of claim 11 wherein said filter circuit includes an edge detection circuit. 
     
     
       14. The apparatus of claim 11 wherein said filter circuit includes a comparison circuit coupled to an edge detection circuit. 
     
     
       15. An apparatus for filtering event signals in a processing system comprising: means for receiving a plurality of event signals from a plurality of event-generating sources;   means for selecting a particular event signal from said plurality of event signals;   means for filtering said selected event signal; and   means for incrementing a counter coupled to said means for filtering said selected event signal.   
     
     
       16. The apparatus of claim 15 wherein said means for filtering said selected event signal includes a comparison circuit for comparing said selected event signal with a counter mask. 
     
     
       17. The apparatus of claim 15 wherein said means for filtering said selected event signal includes an edge detection circuit. 
     
     
       18. The apparatus of claim 15 wherein said means for filtering said selected event signal includes a comparison circuit coupled to an edge detection circuit. 
     
     
       19. A method for filtering event signals in a processing system, said method comprising the steps of: receiving a plurality of event signals from a plurality of event-generating sources;   selecting a particular event signal from said plurality of event signals;   filtering said selected event signal;   generating a filtered event signal; and   incrementing a counter in response to said filtered event signal.   
     
     
       20. The method of claim 19 wherein the step of filtering said selected event signal includes comparing said selected event signal to a counter mask. 
     
     
       21. The method of claim 19 wherein the step of filtering said selected event signal includes detecting an edge of said selected event signal.